This research will use a Drosophila model system to study the Bcr-Abl signal transduction pathway. The immediate goal of this project is to take advantage of the power of Drosophila genetics to identify and characterize conserved downstream targets of Bcr-Abl and thus to elucidate the mechanism of action of Bcr-Abl. The broad, long term goal of this work will be to take what is learned in the Drosophila model system and apply it to mammalian systems to look for mammalian homologs of the Bcr-Abl enhancers and suppressors that are identified in mutagenesis screens carried out in flies. The model system is based on the finding that transgenic Drosophila expressing Bcr-Abl in the developing eye imaginal disk develop into viable adult flies with a dominant, easily-scored, rough eye phenotype. TO identify potential downstream targets of Bcr-Abl, genetic modifier screens for enhancers and suppresors of the Bcr-Abl rough eye phenotype have been carried out using three approaches, chemical mutagenesis, ray mutagenesis and survey of 295 large deficiencies that span 61% of the second and third chromosomes (2nd and 3rd chromosome deficiency kits). Two different modifiers, a suppressor mutation and an enhancing deficiency genetically map near two different genes that function upstream of Drosophila JNK. Specific aim 1 is to test the hypothesis that these two modifiers perturb Bcr-Abl signaling thru the JNK/stress kinase pathway. Specific aim 2 describes how suppressor and enhancers recovered in modifier screens will be prioritized, identified and clones. A third aim proposes genetic, molecular and biochemical characterization of enhancer and suppressor molecules and should contribute to the understanding of the mechanism of Bcr-Abl mediated oncogenesis. A fourth aim proposes to test whether identified and cloned modifiers can enhance or suppress the Bcr-Abl transformed phenotype of a Bcr-Abl transformed mammalian cell line. Identification of Bcr-Abl downstream targets will contribute to our understanding of the mechanism of Bcr-Abl oncogenesis and may provide additional sites for intervention therapies of bcr-abl positive CML and ALL.